66824 - DNS: IPv6: does not try all (ip4,ip6) addresses

Status: VERIFIED DUPLICATE of bug 66872

(Core :: Networking, defect)

Description

[Nick Sayer]

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; FreeBSD 5.0-CURRENT i386; en-US; 0.7)
Gecko/20010123
BuildID:    0.7

If I build mozilla with IPv6 support, everything works so long as any hosts that
have aaaa records also listen for requests on those addresses. mozilla never
seems to want to fail over to ipv4 (A records) if none of the available AAAA
records wors.


Reproducible: Always
Steps to Reproduce:
1. Set up a machine with both A and AAAA records in DNS.

2. Set up a web server (or IMAP or POP or NNTP... Protocol does not matter), but
force it to bind only to IPv4 ports.

3. Attempt to view pages on that server.

Actual Results:  If DNS reports both A and AAAA records for the host in
question, the A records will never be tried.

Expected Results:  It may be the case that IPv6 should be tried before IPv4.
That is a policy issue not addressed here. It certainly makes the Dancing Kame
(www.kame.net) a good test if IPv6 is tried first. But after trying all of the
AAAA records once and failing, mozilla should then move on to the A records and
attempt an ipv4 connection. It does not ever seem to do so.

It is not reasonable to not attempt ALL available alternatives, even if trying
some means trying a different protocol, even if it is inconvenient to do so.

Comment 1

[Boris Zbarsky [:bzbarsky]]

There is already a bug on this issue.  marking as duplicate.

Thank you for the clear and informative bug report!

*** This bug has been marked as a duplicate of 66872 ***

Comment 2

[Tom Everingham]

verified dup

Comment 3

[Michael Nix]

Also a problem on when the ip6 address is unreachable - eg both machines have
ip6 and are on the same network - works... when  one machine is moved to another
network with an ip4 only VPN connection between them, it fails. Would be nice if
it at least gave an error, rather than just doing nothing.